A typical example of construction machines is a hydraulic excavator. A hydraulic excavator includes a work implement assembly (front work implement assembly), a swing structure to which a boom base end of the work implement assembly is mounted, and a track structure provided below the swing structure. The work implement assembly includes a boom, an arm, and a bucket (a plurality of driven members), each able to rotate about an approximately horizontal rotating shaft, that are connected together. In a hydraulic excavator, the driven members such as the boom are each operated with a control lever (operating unit) that controls a driving direction and driving speed. When the control lever is operated, the driven member makes a rotating motion about a rotating shaft. As a result, when one of the driven members is operated with the control lever, for example, a tip of the bucket basically traces a circular path. In order to form a planar excavation surface with the hydraulic excavator, for example, by leveling the bucket, therefore, operation of the control lever is complicated, requiring considerable skills and experience.
For this reason, a device that facilitates such a task (area limiting excavation control system) is disclosed in JP-3056254 B. The present document discloses an area limiting excavation control system for hydraulic excavators, configured as follows. The work area limiting excavation control system accepts, in advance, a setting as to an area within which a front work implement assembly can move. The control system calculates, with a control unit, a position and a posture of the front work implement assembly based on a signal supplied from an angle sensor and calculates a target speed vector of the work implement assembly based on a signal supplied from an operating unit. The control system maintains the target speed vector unchanged when the front work implement assembly is within the set area but not close to a boundary thereof. The control system corrects the target speed vector such that a vector component in the direction of approaching the boundary of the set area is reduced when the front work implement assembly is within the set area and close to the boundary thereof. The control system corrects the target speed vector such that the front work implement assembly goes back into the set area when the front work implement assembly is outside the boundary of the set area. This allows excavation to be conducted within a limited area in a highly efficient and smooth manner. As a result, the area set in advance serves as a basic movable range of the bucket, thus facilitating excavation along the boundary of the area irrespective of operator's degree of skill.